Storing items and retrieving items (e.g., to fill discrete customer orders) can be laborious and time consuming. Many large organizations have extensive storage areas in which numerous and diverse items are stored and/or from which they are retrieved. Sorting and retrieving items from the hundreds or thousands of storage areas requires significant labor to perform manually.
By way of illustrative example, some automated storage and retrieval (ASR) systems utilize one or more three dimensional rack structures wherein each defines a first array of storage spaces and a second array of storage spaces. In such systems, the rack structure defines an aisle which extends the length and height of the two storage space arrays so that a storage container can be individually transported to, and inserted into, any vacant storage space of either array. Conversely, any storage container already disposed in one of the storage spaces of either array can be extracted and transported to a remote destination such, for example, as a picking station where a worker picks items from the storage containers.